An inverted index

I collect classic mystery novels, traditional British detective tales. These quaint, almost a century old puzzles have a soothing effect on me.

I do maintain a text file catalogue though (arrgh… no database for such a simple thing; a text file would do). The database I have is a csv file with the author surnames and then the book titles. Now, what if I want to reread a book again but can't remember its full name or the author name? In such a scenario, we would use an inverted index to find the complete name.

An inverted index is when you remember a word in the title and seem to look up the author's name. The following Java program prints the inverted index for a few of these books:

class AuthorAndTitle {  // 1
  private final String authName;
  private final String title;

  public AuthorAndTitle(String authName, String title) {
    super();
    this.authName = authName;
    this.title = title;
  }

  public String getAuthName() {
    return authName;
  }

  public String...